The use of tobacco products is one of leading causes of preventable death worldwide. The psychoactive effects of tobacco have been attributed primarily to its content of the bioactive substance nicotine. Current therapies decrease the withdrawal symptoms that occur in addicted individuals upon cessation of nicotine intake. However, this approach has had only moderate success rates in reducing relapse in addicted individuals and does not reverse the biochemical changes that occur in the central nervous system after repeated nicotine use. Endocannabinoid (eCB) signaling has been implicated in modulating the induction and expression of reward-related behaviors for nicotine and nearly all other known drugs of abuse, yet our understanding of the roles of specific eCBs that are involved in nicotine reward remains unclear. Interestingly, combined inhibition of monoacylglycerol lipase (MAGL) and fatty acid acyl hydrolase (FAAH), which degrade distinct sets of eCBs, can mimic the classic cannabinoid behaviors caused by tetrahydrocannabinol (THC), whereas inhibiting each pathway alone only causes a unique partial THC-like response. Thus, individual eCBs likely underlie distinct behavioral phenomena, and modulating these pathways may have different therapeutic outcomes. This project will focus on elucidating the specific eCB signaling mechanisms that reinforce nicotine self-administration in rats, as well as the therapeutic potential of FAAH and MAGL inhibition. Aim 1 will evaluate the effect of selective FAAH and MAGL inhibitors on nicotine self-administration. Aim 2 will characterize eCB changes induced by nicotine self-administration. Using this information, Aim 3 will investigate the receptor mechanisms through which eCBs modulate nicotine self-administration. The overall goal of the experiments described here is to characterize eCB-receptor mechanisms reinforcing nicotine behavior, as well as the effects of eCB clearance inhibition (FAAH and MAGL) on nicotine self- administration behavior. A better understanding of these processes should lead to innovative therapies that have direct impact and clinical relevance for reducing nicotine use in addicted individuals.